Is the sale that took place between the friend's father and the swindler valid or void, and is the questioner's purchase of this shop valid or void?

To research the ruling on selling the aforementioned apartment, the reason why the seller did not obtain the title deed must be known. If the apartment is mortgaged, selling it without the mortgagee's permission is a matter of scholarly disagreement: some deem it void, while others consider it valid but contingent upon the mortgagee's approval.

If we adopt the second opinion (the validity of the sale being contingent on the mortgagee's approval), the first sale is considered valid and enforceable with the mortgagee's approval. In this case, it is not permissible for the inquirer to buy the apartment from his friend, as it is no longer his property. Whatever income the first buyer received from rent belongs to him.

However, if we adopt the first opinion (the nullity of the sale), the sale is void, and the buyer must return the apartment and its proceeds to the owner.

The preponderant opinion is that selling a mortgaged item is valid and enforceable if it is done with the mortgagee's consent. The owner's retraction from selling the mortgaged item does not invalidate the sale, because it is valid and binding upon him.

The mentioned law is incorrect, because if a sale is concluded meeting its conditions and pillars, ownership transfers to the buyer. It is then impermissible for anyone to buy the sold item thereafter, based on the hadith: "None of you should sell over the sale of his brother." The second sale is void, and the title deed is for documentation and does not invalidate the right of the first buyer.